// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab

#include <errno.h>

#include "common/ceph_context.h"
#include "common/dout.h"
#include "common/Mutex.h"
#include "common/WorkQueue.h"
#include "include/Context.h"
#include "include/rados/librados.hpp"
#include "include/rbd/librbd.hpp"

#include "librbd/ExclusiveLock.h"
#include "librbd/ImageCtx.h"
#include "librbd/internal.h"
#include "librbd/LibrbdWriteback.h"
#include "librbd/ObjectMap.h"
#include "librbd/Journal.h"
#include "librbd/Utils.h"
#include "librbd/io/AioCompletion.h"
#include "librbd/io/ObjectRequest.h"

#include "include/assert.h"

#define dout_subsys ceph_subsys_rbd
#undef dout_prefix
#define dout_prefix *_dout << "librbdwriteback: "

namespace librbd {

  /**
   * callback to finish a rados completion as a Context
   *
   * @param c completion
   * @param arg Context* recast as void*
   */
  void context_cb(rados_completion_t c, void *arg)
  {
    Context *con = reinterpret_cast<Context *>(arg);
    con->complete(rados_aio_get_return_value(c));
  }

  /**
   * context to wrap another context in a Mutex
   *
   * @param cct cct
   * @param c context to finish
   * @param l mutex to lock
   */
  class C_ReadRequest : public Context {
  public:
    C_ReadRequest(CephContext *cct, Context *c, Mutex *cache_lock)
      : m_cct(cct), m_ctx(c), m_cache_lock(cache_lock) {
    }
    void finish(int r) override {
      ldout(m_cct, 20) << "aio_cb completing " << dendl;
      {
        Mutex::Locker cache_locker(*m_cache_lock);
	m_ctx->complete(r);
      }
      ldout(m_cct, 20) << "aio_cb finished" << dendl;
    }
  private:
    CephContext *m_cct;
    Context *m_ctx;
    Mutex *m_cache_lock;
  };

  class C_OrderedWrite : public Context {
  public:
    C_OrderedWrite(CephContext *cct, LibrbdWriteback::write_result_d *result,
		   const ZTracer::Trace &trace, LibrbdWriteback *wb)
      : m_cct(cct), m_result(result), m_trace(trace), m_wb_handler(wb) {}
    ~C_OrderedWrite() override {}
    void finish(int r) override {
      ldout(m_cct, 20) << "C_OrderedWrite completing " << m_result << dendl;
      {
	Mutex::Locker l(m_wb_handler->m_lock);
	assert(!m_result->done);
	m_result->done = true;
	m_result->ret = r;
	m_wb_handler->complete_writes(m_result->oid);
      }
      ldout(m_cct, 20) << "C_OrderedWrite finished " << m_result << dendl;
      m_trace.event("finish");
    }
  private:
    CephContext *m_cct;
    LibrbdWriteback::write_result_d *m_result;
    ZTracer::Trace m_trace;
    LibrbdWriteback *m_wb_handler;
  };

  struct C_WriteJournalCommit : public Context {
    typedef std::vector<std::pair<uint64_t,uint64_t> > Extents;

    ImageCtx *image_ctx;
    std::string oid;
    uint64_t object_no;
    uint64_t off;
    bufferlist bl;
    SnapContext snapc;
    uint64_t journal_tid;
    ZTracer::Trace trace;
    Context *req_comp;
    bool request_sent = false;

    C_WriteJournalCommit(ImageCtx *_image_ctx, const std::string &_oid,
                         uint64_t _object_no, uint64_t _off,
                         const bufferlist &_bl, const SnapContext& _snapc,
                         uint64_t _journal_tid,
			 const ZTracer::Trace &trace, Context *_req_comp)
      : image_ctx(_image_ctx), oid(_oid), object_no(_object_no), off(_off),
        bl(_bl), snapc(_snapc), journal_tid(_journal_tid),
        trace(trace), req_comp(_req_comp) {
      CephContext *cct = image_ctx->cct;
      ldout(cct, 20) << this << " C_WriteJournalCommit: "
                     << "delaying write until journal tid "
                     << journal_tid << " safe" << dendl;
    }

    void complete(int r) override {
      if (request_sent || r < 0) {
        if (request_sent && r == 0) {
          // only commit IO events that are safely recorded to the backing image
          // since the cache will retry all IOs that fail
          commit_io_event_extent(0);
        }

        req_comp->complete(r);
        delete this;
      } else {
        send_request();
      }
    }

    void finish(int r) override {
    }

    void commit_io_event_extent(int r) {
      CephContext *cct = image_ctx->cct;
      ldout(cct, 20) << this << " C_WriteJournalCommit: "
                     << "write committed: updating journal commit position"
                     << dendl;

      // all IO operations are flushed prior to closing the journal
      assert(image_ctx->journal != NULL);

      Extents file_extents;
      Striper::extent_to_file(cct, &image_ctx->layout, object_no, off,
                              bl.length(), file_extents);
      for (Extents::iterator it = file_extents.begin();
           it != file_extents.end(); ++it) {
        image_ctx->journal->commit_io_event_extent(journal_tid, it->first,
                                                   it->second, r);
      }
    }

    void send_request() {
      CephContext *cct = image_ctx->cct;
      ldout(cct, 20) << this << " C_WriteJournalCommit: "
                     << "journal committed: sending write request" << dendl;

      assert(image_ctx->exclusive_lock->is_lock_owner());

      request_sent = true;
      auto req = new io::ObjectWriteRequest(image_ctx, oid, object_no, off,
                                            bl, snapc, 0, trace, this);
      req->send();
    }
  };

  struct C_CommitIOEventExtent : public Context {
    ImageCtx *image_ctx;
    uint64_t journal_tid;
    uint64_t offset;
    uint64_t length;

    C_CommitIOEventExtent(ImageCtx *image_ctx, uint64_t journal_tid,
                          uint64_t offset, uint64_t length)
      : image_ctx(image_ctx), journal_tid(journal_tid), offset(offset),
        length(length) {
    }

    void finish(int r) override {
      // all IO operations are flushed prior to closing the journal
      assert(image_ctx->journal != nullptr);

      image_ctx->journal->commit_io_event_extent(journal_tid, offset, length,
                                                 r);
    }
  };

  LibrbdWriteback::LibrbdWriteback(ImageCtx *ictx, Mutex& lock)
    : m_tid(0), m_lock(lock), m_ictx(ictx) {
  }

  void LibrbdWriteback::read(const object_t& oid, uint64_t object_no,
			     const object_locator_t& oloc,
			     uint64_t off, uint64_t len, snapid_t snapid,
			     bufferlist *pbl, uint64_t trunc_size,
			     __u32 trunc_seq, int op_flags,
                             const ZTracer::Trace &parent_trace,
                             Context *onfinish)
  {
    // on completion, take the mutex and then call onfinish.
    Context *req = new C_ReadRequest(m_ictx->cct, onfinish, &m_lock);

    {
      RWLock::RLocker snap_locker(m_ictx->snap_lock);
      if (m_ictx->object_map != nullptr &&
          !m_ictx->object_map->object_may_exist(object_no)) {
        m_ictx->op_work_queue->queue(req, -ENOENT);
	return;
      }
    }

    librados::ObjectReadOperation op;
    op.read(off, len, pbl, NULL);
    op.set_op_flags2(op_flags);
    int flags = m_ictx->get_read_flags(snapid);

    librados::AioCompletion *rados_completion =
      util::create_rados_callback(req);
    int r = m_ictx->data_ctx.aio_operate(
      oid.name, rados_completion, &op, flags, nullptr,
      (parent_trace.valid() ? parent_trace.get_info() : nullptr));
    rados_completion->release();
    assert(r >= 0);
  }

  bool LibrbdWriteback::may_copy_on_write(const object_t& oid, uint64_t read_off, uint64_t read_len, snapid_t snapid)
  {
    m_ictx->snap_lock.get_read();
    librados::snap_t snap_id = m_ictx->snap_id;
    m_ictx->parent_lock.get_read();
    uint64_t overlap = 0;
    m_ictx->get_parent_overlap(snap_id, &overlap);
    m_ictx->parent_lock.put_read();
    m_ictx->snap_lock.put_read();

    uint64_t object_no = oid_to_object_no(oid.name, m_ictx->object_prefix);

    // reverse map this object extent onto the parent
    vector<pair<uint64_t,uint64_t> > objectx;
    Striper::extent_to_file(m_ictx->cct, &m_ictx->layout,
			  object_no, 0, m_ictx->layout.object_size,
			  objectx);
    uint64_t object_overlap = m_ictx->prune_parent_extents(objectx, overlap);
    bool may = object_overlap > 0;
    ldout(m_ictx->cct, 10) << "may_copy_on_write " << oid << " " << read_off
			   << "~" << read_len << " = " << may << dendl;
    return may;
  }

  ceph_tid_t LibrbdWriteback::write(const object_t& oid,
				    const object_locator_t& oloc,
				    uint64_t off, uint64_t len,
				    const SnapContext& snapc,
				    const bufferlist &bl,
				    ceph::real_time mtime, uint64_t trunc_size,
				    __u32 trunc_seq, ceph_tid_t journal_tid,
                                    const ZTracer::Trace &parent_trace,
				    Context *oncommit)
  {
    ZTracer::Trace trace;
    if (parent_trace.valid()) {
      trace.init("", &m_ictx->trace_endpoint, &parent_trace);
      trace.copy_name("writeback " + oid.name);
      trace.event("start");
    }

    uint64_t object_no = oid_to_object_no(oid.name, m_ictx->object_prefix);

    write_result_d *result = new write_result_d(oid.name, oncommit);
    m_writes[oid.name].push(result);
    ldout(m_ictx->cct, 20) << "write will wait for result " << result << dendl;
    C_OrderedWrite *req_comp = new C_OrderedWrite(m_ictx->cct, result, trace,
                                                  this);

    // all IO operations are flushed prior to closing the journal
    assert(journal_tid == 0 || m_ictx->journal != NULL);
    if (journal_tid != 0) {
      m_ictx->journal->flush_event(
        journal_tid, new C_WriteJournalCommit(
	  m_ictx, oid.name, object_no, off, bl, snapc, journal_tid, trace,
          req_comp));
    } else {
      auto req = new io::ObjectWriteRequest(
	m_ictx, oid.name, object_no, off, bl, snapc, 0, trace, req_comp);
      req->send();
    }
    return ++m_tid;
  }


  void LibrbdWriteback::overwrite_extent(const object_t& oid, uint64_t off,
					 uint64_t len,
					 ceph_tid_t original_journal_tid,
                                         ceph_tid_t new_journal_tid) {
    typedef std::vector<std::pair<uint64_t,uint64_t> > Extents;

    ldout(m_ictx->cct, 20) << __func__ << ": " << oid << " "
                           << off << "~" << len << " "
                           << "journal_tid=" << original_journal_tid << ", "
                           << "new_journal_tid=" << new_journal_tid << dendl;

    uint64_t object_no = oid_to_object_no(oid.name, m_ictx->object_prefix);

    // all IO operations are flushed prior to closing the journal
    assert(original_journal_tid != 0 && m_ictx->journal != NULL);

    Extents file_extents;
    Striper::extent_to_file(m_ictx->cct, &m_ictx->layout, object_no, off,
			    len, file_extents);
    for (Extents::iterator it = file_extents.begin();
	 it != file_extents.end(); ++it) {
      if (new_journal_tid != 0) {
        // ensure new journal event is safely committed to disk before
        // committing old event
        m_ictx->journal->flush_event(
          new_journal_tid, new C_CommitIOEventExtent(m_ictx,
                                                     original_journal_tid,
                                                     it->first, it->second));
      } else {
        m_ictx->journal->commit_io_event_extent(original_journal_tid, it->first,
					        it->second, 0);
      }
    }
  }

  void LibrbdWriteback::complete_writes(const std::string& oid)
  {
    assert(m_lock.is_locked());
    std::queue<write_result_d*>& results = m_writes[oid];
    ldout(m_ictx->cct, 20) << "complete_writes() oid " << oid << dendl;
    std::list<write_result_d*> finished;

    while (!results.empty()) {
      write_result_d *result = results.front();
      if (!result->done)
	break;
      finished.push_back(result);
      results.pop();
    }

    if (results.empty())
      m_writes.erase(oid);

    for (std::list<write_result_d*>::iterator it = finished.begin();
	 it != finished.end(); ++it) {
      write_result_d *result = *it;
      ldout(m_ictx->cct, 20) << "complete_writes() completing " << result
			     << dendl;
      result->oncommit->complete(result->ret);
      delete result;
    }
  }
}